‰  NOW 40 WPM  ‰  TEXT IS FROM MAY 2015  QST  PAGE 41 ‰
SUMMARY, MY DATA SHOWS THAT THE FIRST DIT WOULD ALWAYS TRIGGER THE 1420 HZ
ECHO, BUT 2R5 SECONDS MUST PASS BEFORE I OBSERVED ANOTHER 1420 HZ ECHO
EVENT.  APPARENTLY IT WAS THE TOTAL ELAPSED TIME BETWEEN DITS THAT WAS
IMPORTANT, RATHER THAN THE NUMBER OF DITS TRANSMITTED.  THE STATION AND
EQUIPMENT  I OBSERVED THE ECHOES USING A YAESU FT DX 5000 TRANSCEIVER WITH
FULL BREAK IN ENABLED MINIMUM RECOVERY DELAY AND THE AUTOMATIC GAIN CONTROL
AGC OFF.  I HAD TURNED OFF ALL DIGITAL A

CAUSING A 5 MS GAP IN RECEIVER NOISE FOLLOWED BY A NEGATIVE AMPLITUDE
EXCURSION OF THE BASELINE LASTING FROM 65R2 MS TO 126R1 MS.  THAT EVENT
MARKS THE TRANSMISSION OF THE 60R9 MS DIT DURATION.  THE TRANSCEIVER
RECOVERS FROM TRANSMIT TO RECEIVE MODE BETWEEN 126R1 AND 182R5 MS, AND THE
RECEIVER IS BACK ON AT 182R5 MS.  A RETURN PULSE SHORT DELAYED ECHO STARTS
AT APPROXIMATELY 217R4 MS AND ENDS AT 277R8 MS, FOLLOWED BY MORE RECEIVER
NOISE.  THE TRANSMITTED PULSE WIDTH WAS APPROXIMATELY 60R9 MS.  I ESTIMATED
THE ECHO PULSE DURATION AS 60R4 MS, WHICH IS VERY CLOSE TO THE TRANSMITTED
PULSE WIDTH.  PICKING START AND END TIMES OF THE ECHO IN THE PRESENCE OF
NOISE IS NOT EXACT.  THE DELAY BETWEEN TRANSMISSION AND ECHO RECEPTION WAS
APPROXIMATELY 152R2 MS.  BY COMPARISON, PROPAGATION DELAY TIME FOR A TRIP
AROUND EARTH OR HALFWAY AND BACK IS SLIGHTLY LONGER THAN 138 MS.  MY
EARLIER REPORT ON 80 METER BAND SHORT DELAYED ECHO OBSERVATIONS APPEARED IN
THE JUNE 2007 ISSUE OF QST.  SEVERAL AMATEURS RESPONDED IN QSTS MARCH 2009
TECHNICAL CORRESPONDENCE COLUMN, AND PROVIDED SEVERAL POSSIBLE EXPLANATIONS
FOR ECHOES WITH TIME DELAYS LONGER THAN A SIGNAL GOING AROUND EARTH.  A

SHORT DELAYED ECHOES CONTINUE TO AMAZE SHORT DELAYED ECHOES CONTINUE TO
AMAZE  SOME, BUT NOT ALL, TRANSMISSIONS PRODUCE ECHOES AT TWO FREQUENCIES.
GENE GRENEKER, K4MOG  ON JANUARY 7, 2013, BETWEEN 220 PM AND 300 PM EST, I
HEARD SHORT DELAYED ECHOES WHILE CALLING CQ ON 18R090 MHZ CW.  I HAVE HEARD
SHORT DELAYED ECHOES BEFORE ON 80 METERS.  MANY AMATEURS HAVE REPORTED BOTH
SHORT AND LONG DELAYED ECHOES, AND A BODY OF LITERATURE DISCUSSES THE
SOURCE OF THESE EVENTS, SO THERE IS NOTHING NEW ABOUT SHORT DELAYED ECHOES,
RIGHT?  WRONG.  WHEN I HEARD THE SHORT DELAYED ECHOES, I STARTED KEYING
SPECIFIC PATTERNS OF MORSE CODE DITS TO EXCITE THE ECHOES FOR RECORDING AND
LATER ANALYSIS.  EACH TIME I SENT A DIT, I COULD HEAR A 675 HZ SHORT
DELAYED RETURN ECHO MY RECEIVE FREQUENCY WAS OFFSET 675 HZ HIGHER THAN MY
TRANSMIT FREQUENCY.  NOW FOR THE INTERESTING PART FOLLOWING EVERY FOURTH
DIT IN THE SEQUENCE, I NOTICED TWO ECHOES ONE AT 675 HZ AND THE SECOND AT
APPROXIMATELY 1420 HZ, SLIGHTLY MORE THAN TWICE THE FIRST ECHO FREQUENCY.
I SENT DITS AT HALF SECOND INTERVALS, THEN AT OTHER TIMINGS OVER THE NEXT
40 MINUTES.  MY ANALYSIS OF THE RECORDED DATA PRODUCED RESULTS THAT I
COULDNT EXPLAIN.  MEASURED ECHOES FIGURE 1 SHOWS A SIGNAL EVENT TIMELINE.
FROM LEFT TO RIGHT, RECEIVER NOISE IS EVIDENT BETWEEN STARTING TIME 0 TO
APPROXIMATELY 60 MS.  AT ABOUT 60 MS I KEYED THE TRANSCEIVER WITH A DIT
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ